A Digital Rights Management (DRM) system is a technology for securely protecting and systematically managing a rights object of digital contents, and provides a series of protection and management systems related to the prevention of illegal copy of digital contents and acquisition of rights object of the digital contents, generation and circulation of the digital contents, and procedures of use of the digital contents. The DRM has been applied to a variety of applications, such as a media player, an audio player, an image viewer, and the like.
FIG. 1 is a schematic view of a digital rights management system. The digital rights management system controls digital contents provided from a contents provider to a user such that the user is able to use the digital contents as much as rights object granted to the user. Here, the contents provider is an entity corresponding to a Contents Issuer (CI) and/or a Rights Issuer (RI).
The Contents Issuer (CI) issues contents (i.e., DRM contents) protected using a specific encoding key so as to protect the DRM contents from users having no access rights, and the Rights Issuer (RI) issues Rights Object (RO) required to use the protected contents.
A DRM agent installed in a terminal receives the protected contents and rights object, and controls a use of the contents by analyzing a license included in the rights object and converting the protected contents into a form suitable for being used in a corresponding terminal.
FIG. 2 is a signal flowchart illustrating a related art method for moving, by a first terminal (a terminal of a first user), a rights object occupied by the first terminal to a second terminal (a terminal of a second user) through an RI. The first terminal is a source terminal which desires to move a rights object, while the second terminal is a target terminal which receives the rights object. In the related art shown in FIG. 2, after receiving a trigger message for moving a rights object from an RI (S1), the first terminal sends a request message (MoveRightsRequest) for moving a rights object (e.g., RO1, RO2 and RO3) occupied by (belonging to) the first terminal (S2). The RI sends to the first terminal a message (MoveRightsResponse) in response to the request message (S3), and moves the rights object (i.e., RO1, RO2 and RO3) requested by the first terminal to the second terminal (S4).
In the related art as shown in FIG. 2, the source terminal moves the rights object occupied by the source terminal to the target terminal through the RI, however, requirements for moving the rights object of the source terminal, etc. are not considered.